Precancerous skin lesions

Actinic keratosis

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• Definition: UV-induced precancerous skin lesion that may progress to skin cancer.
• Epidemiology: occurs especially in individuals with light skin who are over the age of 50
• Etiology: sun exposure (e.g., from working outdoors)
• Lesion
  • Occurs on areas of sun-exposed skin
  • Initially: small lesion (papule or plaque) with rough surface (sandpaper-like texture)
  • Later: Lesions grow and become brown or erythematous and scaly.
  • Hyperkeratosis in such lesions may become prominent and form cutaneous horns.
• Pathology
  • Parakeratosis: Retention of nuclei in the stratum corneum. t
  • Atypical keratinocytes: Confined to the basal layer of the epidermis (partial thickness dysplasia).
    • Note: If full-thickness dysplasia → Squamous Cell Carcinoma in situ (Bowen disease).
  • Solar elastosis (blue-gray degeneration of collagen) in the dermis.
• Management:
  • Isolated / Few lesions: Cryotherapy (liquid nitrogen) or surgical curettage/shave.
  • Multiple / Field cancerization: Topical 5-Fluorouracil (5-FU) or topical imiquimod (warn pts about expected erythema/crusting); photodynamic therapy (PDT) is second-line.
  • Prevention: Daily broad-spectrum sunscreen (SPF ≥ 30) and sun avoidance.
• Prognosis
  • Lesions may either regress, persist, or progress to cutaneous squamous cell carcinoma (SCC).
  • The degree of epithelial dysplasia determines the risk of cutaneous squamous cell carcinoma.